Assessment of specific gravity determined by Ames N-Multistix-SG

Specific gravity (SG) was determined in 204 urines by N-Multistix-SG solid phase test strip. Seventy-seven of the urines were from patients with known renal disease or were positive for protein or glucose, or had pH greater than 6.4 (Group I) and were assayed for osmolality, SG by urinometer and refractometer, and several other parameters, intercorrelations were calculated. Osmolality was used as the gold standard. In Group I, correlation of osmolality with N-Multistix SG (r = 0.66) was not significantly different (p greater than 0.1) from that found with SG determined by refractometer (r = 0.72), or urinometer (r = 0.60). The correlation coefficient for 45 N-Multistix-SG values determined by two staff members was 0.91. For the 127 Group II normal urines, the correlation coefficient between Multistix-SG and SG by refractometer was 0.85. Multistix-SG avoids the errors related to large molecules such as glucose and radiographic contrast media seen with SG determined by urinometer and refractometer (uncorrected for glucose) and was found to have comparable accuracy to these two methods when compared with osmolality, in patients with known renal disease or abnormal urinalysis.